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Module 1.6b

Figure 1.6-6
The wavelengths we see
The wide spectrum of
electromagnetic energy ranges
White from gamma rays as short as
light
Prism the diameter of an atom to radio
waves as long as 62 miles (100
kilometers). The wavelengths
visible to the human eye (shown
enlarged) extend from the shorter
blue-violet light waves to the
longer waves of red light.
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400 500 600 700
Part of spectrum visible
to humans

Gamma X-rays Ultra- Infrared Radar Broadcast
rays violet rays bands
rays
10 –5 10 –3 10 –1 10 1 10 3 10 5 10 7 10 9 10 11 10 13
Wavelength in nanometers (billionths of a meter)

Short wavelength = high frequency Great amplitude Figure 1.6-7
(bluish colors) (bright colors)
The physical properties of
waves
(a) Waves vary in wavelength (the
distance between successive
peaks). Frequency, the number of
complete wavelengths that can
Long wavelength = low frequency Small amplitude pass a point in a given amount of
(reddish colors) (dull colors) time, depends on the wavelength.
The shorter the wavelength, the
higher the frequency. Wavelength
determines the perceived color
of light. (b) Waves also vary in
amplitude (the height from peak to
(a) (b) trough). Wave amplitude influences
the perceived brightness of colors.

The iris responds to your cognitive and emotional states. If you have vision, imagine lens the transparent structure
a sunny sky and your iris will constrict; imagine a dark room and it will dilate (Laeng & behind the pupil that changes
Sulutvedt, 2014). The iris also constricts when you feel disgust or you are about to answer shape to help focus images on
No to a question (de Gee et al., 2014; Goldinger & Papesh, 2012). And when you’re feeling the retina.
amorous or trusting, your telltale dilated pupils subtly signal your feelings (Attard-Johnson retina the light-sensitive back
inner surface of the eye, containing
et al., 2016, 2017; Kret & De Dreu, 2017; Prochanzkova et al., 2018). the receptor rods and cones plus
After passing through your pupil, light hits the transparent lens in your eye. The lens then layers of neurons that begin the
focuses the light rays into an image on your retina, the multilayered tissue lining the back inner processing of visual information.
surface of the eyeball. To focus the rays, the lens changes its curvature and thickness in a process

Sensation: Vision Module 1.6b 125

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